I had severe rightsided facial pain with upper toothache. MRI of head shows hypoplastic left maxillary sinus. Did this cause my pain and what is it?

No. The hypoplastic sinus is unrelated to your pain. Could be TMJ or a dental abscess. See oral surgeon for diagnosis. If TMJ, see TMJ expert.
Hypoplasia. Incomplete development or underdevelopment of an organ or tissue. That's what hypoplasia is. It is doubtful that is would cause severe pain, especially on the opposite side of your face. Did you get your teeth thoroughly examined? If not, now is the time to do so.
See OFP expert. Orofacial Pain provides diagnosis and management of pain in the face, mouth (gums, teeth, tongue, etc), TMJ, head, as well as, associated headaches and neck pain. They are the experts in this field. Good luck.

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MRI shows left maxillary sinus blocked, hurts to breath, lip burns a bit on that side. No Trigeminal neuralgia says neurologist. Sinus the cause?

Consult ENT . Pain during breathing could be due to sinus issues but the burning lip isn't usually. Your issues could be a range of things including something like post nasal drip. Have you consulted an ENT physician? That would be where I think you should start. . Read more...